Sonic the Hedgehog (1991)
Sonic the Hedgehog (1991) Title Screen
A screenshot of the title screen of Sonic the Hedgehog

Lead Programmer

Yuji Naka

Development Team(s)

Sonic Team

Game Genre



Sega Megadrive/Genesis

Sonic the Hedgehog is the debut game of the Sonic the Hedgehog franchise, released on June 23rd 1991. It's a platforming game featuring only Sonic and Dr. Robotnik.

Game Development

Note: Much of the game development is already explained in the main Sonic the Hedgehog article. Click on the link to find the information.

Sonic the Hedgehog is for the Megadrive was originally developed to promote the Sega Megadrive/Genesis and rival Nintendo's mascot, Mario. It was created by Sega's AM8 division (renamed as Sonic Team during the development of the game) and presented by Sega. It was to show off the power of the Megadrive, with the large ammount of speed Sonic reaches and the pretty graphics, to boast and destroy Nintendo's NES campaign.


The story of Sonic the Hedgehog is basic. Dr Robotnik is capturing animals from Green Hill Zone and turning them into robots. Sonic must reach Dr Robotnik's stronghold and stop his evil plan.

Chaos Emeralds

Another section to the story are the Chaos Emeralds, which are obtained through the Special Stages. These gems contain miracle powers. If Sonic obtains all 6 of them (7 in later games), Sonic has completely stopped Dr Robotnik and plants and life return to Green Hill Zone. If they are not collected, Dr Robotnik will return to his plans, and at the end of the credits, a picture of Robotnik juggling the Chaos Emeralds will appear, tagged 'TRY AGAIN'.


Sonic the Hedgehog (1991) Green Hill Zone

Sonic in Green Hill Zone, next to a badnik and some rings

Gameplay in Sonic the Hedgehog is 2D side scrolling-platforming. Sonic must jump over spikes and obstacles, or else he'll get hit. If Sonic is hit and possesses no rings, Sonic will die and lose a life. If Sonic is hit with rings collected throughout the stage, 20 of Sonic's rings (if under 20 rings are possessed, that ammount of rings is used in place of 20) will scatter around him, and his ring count will drop to 0. Sonic can collect the rings scattered around him by simply collecting them again, before they dissapear after around 8 seconds.

Also, if Sonic collects 100 rings in any stage, he will earn an Extra Life (1Up).

What is noteable about the physics in the game is the 'momentum based platforming'. This realistically senses when Sonic is moving up a hill or down it, so if Sonic is running up a hill, his momentum decreases at a rate that depends on the steepness of the hill, and vice versa for running down a hill. Momentum based platforming also uses a realistic rate of momentum to build up and lose speed. When jumping, the rate of momentum decreasing is very slow, so Sonic maintains nearly the same speed when jumping as he was previously running without much, or any directional input.

When Sonic jumps, he can attack enemies (called 'badniks) by landing on them. If Sonic lands on a badnik (when the badnik is vulnerable), the badnik will explode, an animal inside will be set free and 100 points is added to his score. If Sonic rebounds off a badnik and lands on another, that score is doubled. If this is repeated, the score will increase by 500, then 1000, then 5000.

Sonic can also use a roll attack. At a high enough speed, while pressing down on the directional pad, Sonic will roll into a ball which can also be used to attack badniks. What is noteable about rolling is that Sonic has a limited speed while running, regardless of momentum from running down a hill. While rolling, however, Sonic's momentum is unlimited, so a huge ammount of speed can be built up when rolling down a steep hill.


There are 7 zones in Sonic the Hedgehog, the first six of them comprising of 3 levels (acts). There is also a boss battle at the end of all the Zones (apart from Scrap Brain Zone). The Final Zone is considered as just a boss battle, with only 1 act and a hallway with a boss at the end.

Zones in Sonic the Hedgehog
Zone name Acts Boss battle? Special Stage accessable? (see Special Stages)
Green Hill Zone 3 Yes Yes
Marble Zone 3 Yes Yes
Spring Yard Zone 3 Yes Yes
Labyrinth Zone 3 Yes Yes
Star Light Zone 3 Yes Yes
Scrap Brain Zone 3 No No
Final Zone 1 Yes No

Special Stages

Special Stage (Sonic 1991)

Sonic in the 1st Special Stage. He is next to the diamonds which form a breakable barrier to the Chaos Emerald

Special Stages in Sonic the Hedgehog see Sonic (in his spin-attack mode) falling through a maze with colourful backgrounds which automatically rotates. Sonic's direction can be influenced by using the Directional Pad. The objective is to reach the end of the stage, where a coloured Chaos Emerald is found. Sonic must dodge certain signs, marked 'GOAL', or else, he will exit the stage and return to the Story Mode. He must also dodge bumpers which will bump him away from his direction (hense the name).

The ring counter is not displayed during Special Stages, although Sonic can collect rings. If he collects 50 rings, Sonic will earn a Continue. If Sonic collects 100 rings, he will earn a 1Up.


When Sonic the Hedgehog was first released, praise for the game came in masses, praising it's speed, level design, incredible graphics and music. Sonic felt refreshing and cool to play at the time, boosting sales of the Megadrive/Genesis incredibly. It soon became so popular, that Sega bundled it in with the Megadrive/Genesis console as the default game. Sonic the Hedgehog is now part of the so-called 'Classic Era', featuring it's sequels, Sonic the Hedgehog 2, 3, CD and Sonic & Knuckles.

Critical reception was mainly the fault of the Special Stages. This included remarks of a wonky jump and the unconsistent difficulty. What was also noted was the 'GOAL' signs, which were thought of as misleading.

Another part of the game which suffered critical reception was the 4th zone, Labyrinth Zone. It was deemed to hard and boring, with Sonic's underwater speed criticised.

Nevertheless, Sonic the Hedgehog is used as a worldwide video gaming benchmark, even to this day.